"We strongly prefer to have one of you as the witness representing Google at the hearing, which will address fundamental questions of business operations rather than merely legal issues," Senator Herb Kohl, a Democrat from Wisconsin, and Senator Michael Lee, a Republican from Utah, wrote in the letter.

While the senators initially asked that one of the executives appear in advance of the August congressional recess, Lee on Friday said Schmidt would testify in September. In a statement, Lee said he was pleased that Schmidt had agreed to testify.

In addition to the scrutiny from the Senate's antitrust subcommittee, Google is facing a review of its business by the US Federal Trade Commission.